Importing LEGO scenes add-on error
The function def loadFromFile(context, filename, isFullFilepath=True) assumes that there is a camera in your scene. It tries to retrieve it, but doesn't check if the returned value is None:

scene  = bpy.context.scene
camera = scene.camera


Later it assigns a location to the camera, which fails when there is no camera in the scene. This causes the exception in line 4337 that you're seeing.

camera.location = mathutils.Vector((6.5, -6.5, 4.75))


You can solve the problem by adding a camera to your scene and setting it as active camera. This issue has been fixed in the 2.80 version of the add-on.